Passive surveillance of human African trypanosomiasis in the Democratic Republic of the Congo: clinical presentation and prospective evaluation of rapid diagnostic and reference laboratory test accuracy

BACKGROUND: Passive screening of gambiense human African trypanosomiasis (HAT) is based on rapid diagnostic tests (RDT), but sensitivity of the currently commercialised RDTs has hardly been assessed prospectively. In view of the increasing importance of remote testing for HAT, the diagnostic performance of reference laboratory tests also needs further documentation.

METHODOLOGY/PRINCIPAL FINDINGS: The study is registered in ClinicalTrials.Gov under identifier NCT03356665. Clinical suspects in 29 health facilities in DR Congo were screened consecutively between October 2017 and December 2020 with 3 HAT RDTs, including HAT Sero K-SeT, an RDT that is nowadays still commercialised. HAT RDT positives were examined parasitologically and their dried blood spots tested in trypanolysis, indirect ELISA/T.b. gambiense, LAMP Trypanosoma brucei Detection Kit and m18S and TgsGp qPCR. Association of clinical signs with HAT, and sensitivity, specificity, and predictive values of the screening and reference laboratory tests were estimated using parasitology as the gold standard. Trypanosomes were detected in 42/3113 study participants. Logistic regression revealed that sleep disruption, enlarged lymph nodes, psychiatric problems, recurrent fever not responding to anti-malarials and motor disorders were significantly associated with HAT (p < 0.05, odds 3.0-10.6). Together, the RDTs detected 253/3113 seropositives. Sensitivity and specificity of HAT Sero K-SeT were respectively 100% (42/42; 95% CI 91.6-100%) and 93.9% (2882/3071; 95% CI 92.9-94.6%). Specificities of the reference laboratory tests were ≥ 91.6%, except for LAMP. Sensitivity of ELISA/T.b. gambiense and trypanolysis were 93.9% (31/33; 95% CI 80.4-98.9) and 84.9% (28/33; 95% CI 69.1-93.4), and were ≤ 63.6% for LAMP, m18S and TgsGp qPCR.

CONCLUSIONS/SIGNIFICANCE: Compared to the WHO's target product profiles for gambiense HAT RDTs, the HAT Sero K-SeT RDT had ideal sensitivity but its specificity was on the borderline of minimally acceptable. Sub-optimal sensitivities of trypanolysis and to a lesser extent, indirect ELISA/T.b. gambiense when applied on DBS, were confirmed. Molecular tests for remote testing need to be improved and evaluated further.